The present invention relates to a one-way clutch of a type employing rollers. This one-way clutch is built into a pulley mounted to auxiliary machinery driven by a crankshaft of an engine of an automobile or the like through a belt, for example.
A conventional one-way clutch of this type is described. An inner annular body and an outer annular body are disposed inside and outside each other in a diameter direction and concentrically with each other. Wedge-shaped spaces each with a gap in a diameter direction narrowing in one direction in a circumferential direction are formed at some positions on a circumference in a gap through which both the annular bodies face each other. A roller is individually disposed in each wedge-shaped space. Between both the annular bodies, a cage having pockets extending to open inside and outside in a diameter direction at positions in phase with the wedge-shaped spaces is provided. Each roller is individually housed by each corresponding pocket. An elastic member is housed by each pocket. Each roller is elastically biased by each elastic member toward a narrower side (lock side) in one direction in the circumferential direction in the wedge-shaped space.
The wedge-shaped spaces are formed by providing cam faces to one of the annular bodies (an outer peripheral face of the inner annular body or an inner peripheral face of the outer annular body) and a wedge angle of the wedge-shaped space is generally set at 9.degree. to 11.degree..
The wedge angle is an angle (.alpha., .beta. which will be described later) at which two tangents intersect each other, one of the tangents being a tangent at a point of contact at which the roller contacts the outer peripheral face of the inner annular body and the other of the tangents being a tangent at a point of contact at which the roller contacts the inner peripheral face of the outer annular body when the roller rolls to the lock side.
In the above structure of the one-way clutch, when each roller rolls to the narrower side in one direction in the circumferential direction of the wedge-shaped space, the clutch is brought into a lock state in which the inner annular body and the outer annular body are integrated with each other through the rollers and rotate synchronously. When each roller rolls to a wider side in the other direction in the circumferential direction of the wedge-shaped space, the clutch is brought into a free state in which the inner annular body and the outer annular body rotate with respect to each other. In this manner, depending on a position in the wedge-shaped space to which each roller rolls, the clutch is switched between the lock state and the free state. In conventional clutches having the above wedge angle, a lock malfunction may occur and a response property of a clutch operation is degraded when the roller rolls to the narrower side of the wedge-shaped space to bring the clutch into the lock state.